The present invention relates to a method of manufacturing a semiconductor device which can be used appropriately for a method of manufacturing a semiconductor device including, e.g., a photolithographic step using a photomask.
In a manufacturing process of a semiconductor device such as a semiconductor integrated circuit device, a photolithographic step is repeatedly performed which irradiates a semiconductor substrate with exposure light via a photomask (hereinafter referred to also as “mask”) having a circuit pattern defined therein to transfer the circuit pattern to a photoresist film formed over the semiconductor substrate.
In recent years, semiconductor devices have been increasingly scaled down so that a method for further shortening the wavelength of exposure light to enhance resolution has been studied. So far, ArF lithography has been developed which uses argon fluoride (ArF) excimer laser light having a wavelength of 193 nm. These days, however, development of EUV lithography using extreme ultraviolet light, i.e., EUV light having a wavelength of 13.5 nm far shorter than the wavelength of the ArF excimer laser light has been promoted.
In the EUV lithography, since the wavelength of the EUV light is extremely short, a transmission-type mask cannot be used, and a reflection-type mask using reflection by a multilayer reflection film made of, e.g., Mo (molybdenum) and Si (silicon) or the like is used.
In addition, the EUV light is absorbed in atmospheric air and the optical intensity thereof significantly attenuates. Therefore, exposure is performed in a state in which the pressure in an exposure device has been reduced. Accordingly, when the EUV mask is held on a mask stage in the exposure device, the EUV mask cannot be held by vacuum suction. The EUV mask is held by electrostatic suction using an electrostatic chuck as the mask stage.
To such an EUV mask, foreign materials (particles) are likely to adhere when the EUV mask is held on a mask stage or when the EUV mask is removed from the mask stage and transported. To remove the adhering foreign materials, cleaning treatment may be performed. In addition, when the EUV mask subjected to the cleaning treatment is stored, measures for preventing contamination or foreign materials from adhering thereto may be taken.
In Japanese Unexamined Patent Publication No. 2011-66258 (Patent Document 1), a technique is described which holds the side surfaces of a mask substrate for an EUV mask or the like, brings a treatment liquid into contact with the surface of the mask substrate to be treated, and ejects gas toward the treatment liquid to separate the treatment liquid from the mask substrate.
In Japanese Unexamined Patent Publication No. Hei 4 (1992)-9950 (Patent Document 2), a technique is described which cleans and dries a photomask, exposes the photomask to a gas atmosphere of hexamethyldisilazane (HMDS) or the like for a given period, and stores the photomask to prevent contamination from developing thereon with time during the storage.